diff --git a/inputfiles/overridingTypes.jsonc b/inputfiles/overridingTypes.jsonc
index 4d1d2822b..2db11d245 100644
--- a/inputfiles/overridingTypes.jsonc
+++ b/inputfiles/overridingTypes.jsonc
@@ -1,14 +1,6 @@
 {
     "mixins": {
         "mixin": {
-            "MessageEventTarget": {
-                "typeParameters": [
-                    {
-                        "name": "T"
-                    }
-                ],
-                "overrideThis": "T"
-            },
             "NavigatorGPU": {
                 "properties": {
                     "property": {
diff --git a/inputfiles/patches/message.kdl b/inputfiles/patches/message.kdl
new file mode 100644
index 000000000..dfcb66828
--- /dev/null
+++ b/inputfiles/patches/message.kdl
@@ -0,0 +1 @@
+interface-mixin MessageEventTarget overrideThis=T typeParameters=T
diff --git a/src/build/patches.ts b/src/build/patches.ts
index 981e50eb0..f7e932847 100644
--- a/src/build/patches.ts
+++ b/src/build/patches.ts
@@ -55,6 +55,17 @@ function handleTyped(type: Node): Typed {
   };
 }
 
+function handleTypeParameters(value: Value) {
+  if (!value) return {};
+  return {
+    typeParameters: [
+      {
+        name: string(value),
+      },
+    ],
+  };
+}
+
 /**
  * Converts patch files in KDL to match the [types](types.d.ts).
  */
@@ -171,6 +182,8 @@ function handleMixinandInterfaces(
     properties: { property },
     methods: { method },
     ...optionalMember("extends", "string", node.properties?.extends),
+    ...optionalMember("overrideThis", "string", node.properties?.overrideThis),
+    ...handleTypeParameters(node.properties?.typeParameters),
     ...interfaceObject,
   } as DeepPartial<Interface>;
 }